The Relationship of Acid Level vs. Sugar Level in Ripening Grapes

Climate

• The most common wine grape is the Vitus vinifera, which grows in U.S. Department of Agriculture hardiness zones 6 to 9. Your climate doesn't just affect which grapes to grow, it also affects how much sugar and acid your grapes will produce while ripening. Warmer climates -- such as Napa, California -- result in a higher sugar content and lower acid. Cooler climates are the reverse; acid levels are higher and sugar levels are lower. Regardless of your climate, however, the desirable levels of sugar and acid to deduce ripeness are the same.

Tartaric and Malic Acid

• You can thank tartaric acid for the tart taste and longevity of wine. Malic acid is the other important factor in a successful harvest. It also contributes to the tart taste and balances sugars, like tartaric acid, but it is far less stable. In the United States, the tartaric acid level is primarily used to determine the overall acidity of grapes before a harvest. The tartaric acid level is measured as a percentage of grams per 100 milliliters.

Brix

• Sugar levels are measured and reported using the term "Brix," a familiar word for wine enthusiasts. Brix is reported as a percentage, in which 1 degree of Brix is equal to 1 gram of sugar for every 100 grams of grape juice. The longer a grape ripens, the higher its sugar content will be, and the lower its acid level will be. As a grape ripens, sugar goes up and acid goes down. In general, the trick to ideal ripeness is waiting until the tartaric acid level is at the lowest point you can risk so that you can maximize your Brix level.

Ripe Levels

• Each type of wine has its own ideal levels. For example, white wine should have Brix levels between 19.5 and 23, with a tartaric acid level of 0.70 to 0.90 percent. Red wine preferably has a higher sugar content level of 20.5 to 23.5 Brix and therefore has a slightly lower tartaric acid level of 0.65 to 0.75 percent. Look up the specific levels for the type of grape you are growing before you test. You can always include a taste test as well when you check for levels, to add your own personal preference into the equation.